Voltage supervisors are employed in many applications to detect over-voltage or under-voltage conditions of a power supply. In one example, the power supply for a mobile device is a battery that is monitored by the voltage supervisor to detect low battery conditions. If the battery voltage drops below a given threshold, the voltage supervisor can detect the condition by comparing the battery voltage to the threshold. The voltage supervisor can then signal the processing elements in the mobile device to alert the user and in very low voltage cases, can initiate an orderly shutdown of the device. One issue with existing voltage supervisor circuits is that they employ resistive voltage dividers to establish the threshold voltage. Such dividers draw current the entire time the device is in operation and thus, over time can cause the battery voltage to drain undesirably.